THE most important point about these four books should be made at the outset. They are not only about the past. They also are about the present and future of biological life on this planet. "Perhaps we are searching for the lessons of our own survival," observes University of Washington (Seattle) fossil sleuth Peter Douglas Ward in explaining the contemporary relevance of his pursuit of "living fossils species that have survived major extinction episodes in the past. It is a theme that runs through all these books. Whether they focus narrowly on the dinosaurs or encompass the full sweep of evolutionary history, these books speak to us of our world today and of our role as a dominant species in it. As paleontologist Niles Eldredge at the American Museum of Natural History in New York City notes: "We think we are removed from nature.... But we will never really escape the natural world...." Some 3.5 billion years of biological and geological evolution have shaped that world. The basic processes and hazards that characterized that long development are still active. Seen in this perspective, it is sobering to realize that humans, with their massive impact on the global environment, have become one of the major hazards. In "On Methuselah's Trail," Ward explores this theme through the testimony of some of the living fossils. He regards survivors such as the horseshoe crabs or the chambered nautilus "as observers and witnesses to the changes in the history of life...." He presents their testimony in essays on his explorations. They are stories of a scientist's intellectual adventures in grappling with one of the mysteries of earthly life - why a few species have survived with little change for tens or hundreds of millions of years. Ward's book lacks the large format and rich, full-color illustration of the other volumes. But his insightful, sprightly writing is colorful enough in its own right. Readers should be aware, however, that he presents a personal view. He readily admits that not all his theories are generally accepted. Nevertheless, his speculation as to why living fossils survived has a ring of truth. Some found refuges. Some have shapes and forms that are successful in spite of massive environmental changes. However, War d adds, "One word sums up the reason for many of the survivals: luck." You can't say that about the dinosaurs. As British paleontologist David Norman of the Nature Conservancy and Oxford University puts it, "Dinosaurs were right for their times but, as always, times change." His book "Dinosaur!" is the companion to the television series with that name. As with "Dinosaurs: a Global View" by Sylvia and Stephen Czerkas, who are associated with the Los Angeles Natural History Museum, the book is a sweeping overview of the dinosaur era. Ongoing research continues to provide unexpected insights into dinosaur development. Today's theories will undoubtedly be outmoded within this decade, as both books make clear. In "Fossils," Niles Eldredge puts the dinosaurs - and humans - into the context of earthly life's 3.5 billion years of evolution. His is an important and informative book. It is also delightfully idiosyncratic. Eldredge and Harvard University's Stephen Jay Gould, who wrote the introduction, developed a controversial theory of species evolution. Roughly put, they view a species as being generally stable but, as circumstances change, it can undergo rapid development into new forms. But this is no scholarly treatise defending an academic argument. It is an essay for everyone interested in the story of earthly life, a marriage of words and illustrations that presents established knowledge and informed speculation. And the illustrations are gems. These are no artist's conceptions but photos of the fossils themselves. They fulfill photographer Murray Alcosser's purpose of presenting fossils "in a way which arouses the curiosity and wonderment of the viewer" because: "Looking at fossils is like peering through a window into the past." All four books highlight the Cretaceous period, 65 million years ago, when an episode of massive extinction with wholesale disappearances on a global scale occurred. Each book explains the uncertainties of the favored theory, which holds that an incoming asteroid or comet was a major contributing factor. Yet all these authors also see that theory as an allegory for our own time. Eldredge notes that climate was deteriorating for millions of years before the event. He observes that the final catastrophe "made a bad situation worse - virtually intolerable, in fact." Turning to our time, he says: "These issues are especially critical when we confront the current wave of extinction affecting our entire planet today.... We are the wild card in the deck, the loose cannon, the modern version, perhaps, of those Cretaceous comets. But we are sentient beings .... Maybe, just maybe, we can see what we are doing, and take steps to mitigate our growing negative impact on the world's ecosystems." It is indeed a sobering thought.